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staking_reward_calculator.go
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staking_reward_calculator.go
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// Copyright (c) 2022 Gobalsky Labs Limited
//
// Use of this software is governed by the Business Source License included
// in the LICENSE.VEGA file and at https://www.mariadb.com/bsl11.
//
// Change Date: 18 months from the later of the date of the first publicly
// available Distribution of this version of the repository, and 25 June 2022.
//
// On the date above, in accordance with the Business Source License, use
// of this software will be governed by version 3 or later of the GNU General
// Public License.
package rewards
import (
"sort"
"code.vegaprotocol.io/vega/core/types"
"code.vegaprotocol.io/vega/libs/num"
"code.vegaprotocol.io/vega/logging"
)
var minThresholdDelegatorReward, _ = num.DecimalFromString("0.001")
// distribute rewards for a given asset account with the given settings of delegation and reward constraints.
func calculateRewardsByStake(epochSeq, asset, accountID string, rewardBalance *num.Uint, valScore map[string]num.Decimal, validatorDelegation []*types.ValidatorData, delegatorShare num.Decimal, maxPayout *num.Uint, log *logging.Logger) *payout {
minLeftOverForDistribution := num.UintZero()
if !maxPayout.IsZero() {
minLeftOverForDistribution, _ = num.UintFromDecimal(minThresholdDelegatorReward.Mul(maxPayout.ToDecimal()))
}
// if there is no reward to give, return no payout
rewards := map[string]*num.Uint{}
totalRewardPayout := num.UintZero()
reward := rewardBalance.Clone()
if reward.IsZero() {
return &payout{
partyToAmount: rewards,
totalReward: totalRewardPayout,
asset: asset,
epochSeq: epochSeq,
}
}
for _, vd := range validatorDelegation {
valScore := valScore[vd.NodeID] // normalised score
if valScore.IsZero() {
// if the validator isn't eligible for reward this round, nothing to do here
continue
}
// how much reward is assigned to the validator and its delegators
epochPayoutForValidatorAndDelegators := valScore.Mul(reward.ToDecimal())
// calculate the fraction delegators to the validator get
totalStakeForValidator := vd.StakeByDelegators.ToDecimal().Add(vd.SelfStake.ToDecimal())
delegatorFraction := delegatorShare.Mul(vd.StakeByDelegators.ToDecimal()).Div(totalStakeForValidator) // totalStakeForValidator must be non zero as valScore is non zero
validatorFraction := num.DecimalFromInt64(1).Sub(delegatorFraction)
// how much delegators take
amountToGiveToDelegators, _ := num.UintFromDecimal(delegatorFraction.Mul(epochPayoutForValidatorAndDelegators))
// calculate the potential reward for delegators and the validator
amountToKeepByValidator, _ := num.UintFromDecimal(validatorFraction.Mul(epochPayoutForValidatorAndDelegators))
log.Info("Rewards: reward calculation for validator",
logging.String("epochSeq", epochSeq),
logging.String("epochPayoutForValidatorAndDelegators", epochPayoutForValidatorAndDelegators.String()),
logging.String("totalStakeForValidator", totalStakeForValidator.String()),
logging.String("delegatorFraction", delegatorFraction.String()),
logging.String("validatorFraction", validatorFraction.String()),
logging.String("amountToGiveToDelegators", amountToGiveToDelegators.String()),
logging.String("amountToKeepByValidator", amountToKeepByValidator.String()))
// check how much reward the validator can accept with the cap per participant
rewardForNode, ok := rewards[vd.PubKey]
if !ok {
rewardForNode = num.UintZero()
}
// if there is no cap just add the total payout for the validator
if maxPayout.IsZero() {
rewards[vd.PubKey] = num.Sum(rewardForNode, amountToKeepByValidator)
totalRewardPayout.AddSum(amountToKeepByValidator)
} else {
balanceWithPayout := num.UintZero().Add(rewardForNode, amountToKeepByValidator)
if balanceWithPayout.LTE(maxPayout) {
rewards[vd.PubKey] = balanceWithPayout
totalRewardPayout.AddSum(amountToKeepByValidator)
} else {
rewards[vd.PubKey] = maxPayout
totalRewardPayout.AddSum(num.UintZero().Sub(maxPayout, rewardForNode))
}
}
log.Info("Rewards: reward kept by validator for epoch (post max payout cap)", logging.String("epoch", epochSeq), logging.String("validator", vd.NodeID), logging.String("amountToKeepByValidator", rewards[vd.PubKey].String()))
remainingRewardForDelegators := amountToGiveToDelegators
// if there's nothing to give to delegators move on
if remainingRewardForDelegators.IsZero() {
continue
}
// calculate the weight of each delegator out of the delegated stake to the validator
delegatorWeights := make(map[string]num.Decimal, len(vd.Delegators))
weightSums := num.DecimalZero()
decimalOne := num.DecimalFromInt64(1)
sortedParties := make([]string, 0, len(vd.Delegators))
for party, delegatorAmt := range vd.Delegators {
delegatorWeight := delegatorAmt.ToDecimal().Div(vd.StakeByDelegators.ToDecimal()) // this is not entered if there are no delegators
weightSums = weightSums.Add(delegatorWeight)
// if the party has 0 delegation, ignore it
if !delegatorAmt.IsZero() {
delegatorWeights[party] = delegatorWeight
sortedParties = append(sortedParties, party)
}
}
sort.Strings(sortedParties)
adjustWeights(delegatorWeights, weightSums, sortedParties, decimalOne)
// calculate delegator amounts
// this may take a few rounds due to the cap on the reward a party can get
// if we still have parties that haven't maxed their reward, they are split the remaining balance
roundsRemaining := 10
for {
log.Info("Reward remaining to distribute to delegators", logging.String("epoch", epochSeq), logging.String("remainingRewardForDelegators", remainingRewardForDelegators.String()))
totalAwardedThisRound := num.UintZero()
for _, party := range sortedParties {
// check if the party has already rewards from other validators or previous rounds (this epoch)
rewardForParty, ok := rewards[party]
if !ok {
rewardForParty = num.UintZero()
}
delegatorWeight := delegatorWeights[party]
rewardAsUint, _ := num.UintFromDecimal(delegatorWeight.Mul(remainingRewardForDelegators.ToDecimal()))
if maxPayout.IsZero() {
totalAwardedThisRound.AddSum(rewardAsUint)
totalRewardPayout.AddSum(rewardAsUint)
rewards[party] = num.UintZero().Add(rewardForParty, rewardAsUint)
} else {
balanceWithPayout := num.UintZero().Add(rewardForParty, rewardAsUint)
if balanceWithPayout.LTE(maxPayout) {
rewards[party] = balanceWithPayout
totalAwardedThisRound.AddSum(rewardAsUint)
totalRewardPayout.AddSum(rewardAsUint)
} else {
rewards[party] = maxPayout
totalAwardedThisRound.AddSum(num.UintZero().Sub(maxPayout, rewardForParty))
totalRewardPayout.AddSum(num.UintZero().Sub(maxPayout, rewardForParty))
}
}
}
roundsRemaining--
// if we finished a round without distributing anything, we should stop
// if this is the final round, stop
// if the left over is too small for retrying to distribute, stop
remainingRewardForDelegators = num.UintZero().Sub(remainingRewardForDelegators, totalAwardedThisRound)
if roundsRemaining == 0 || remainingRewardForDelegators.LT(minLeftOverForDistribution) || totalAwardedThisRound.IsZero() {
break
}
}
}
if totalRewardPayout.GT(rewardBalance) {
log.Error("The reward payout is greater than the reward balance, this should never happen", logging.String("reward-payout", totalRewardPayout.String()), logging.String("reward-balance", rewardBalance.String()))
}
return &payout{
fromAccount: accountID,
partyToAmount: rewards,
totalReward: totalRewardPayout,
asset: asset,
epochSeq: epochSeq,
}
}
func adjustWeights(delegatorWeights map[string]num.Decimal, weightSums num.Decimal, sortedParties []string, decimalOne num.Decimal) {
// NB: due to rounding errors this sum can be greater than 1
// to avoid overflow, we choose the one with the highest weight, if that's not sufficient, we'll again choose the one with the highest weight and adjust
// it marginally until convergence.
for weightSums.GreaterThan(decimalOne) {
precisionError := weightSums.Sub(decimalOne)
maxWeight := num.DecimalZero()
maxWeightParty := ""
for _, p := range sortedParties {
if delegatorWeights[p].GreaterThan(maxWeight) {
maxWeight = delegatorWeights[p]
maxWeightParty = p
}
}
delegatorWeights[maxWeightParty] = num.MaxD(num.DecimalZero(), delegatorWeights[maxWeightParty].Sub(precisionError))
weightSums = num.DecimalZero()
for _, d := range delegatorWeights {
weightSums = weightSums.Add(d)
}
}
}